Helianthus giganteus
giant sunflower
A clump-forming perennial, up to 2.5m in height, with narrow, coarse green leaves and small flowers in late summer and early autumn, with dark yellow centres and yellow ray florets on dark reddish to green stems
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Size
Ultimate height
2.5–4 metresTime to ultimate height
1–2 yearsUltimate spread
1–1.5 metresGrowing conditions
Moisture
Moist but well–drained, Well–drainedpH
Neutral, AlkalineColour & scent
| Stem | Flower | Foliage | Fruit | |
| Spring | Green Red | Green | ||
|---|---|---|---|---|
| Summer | Green Red | Yellow | Green | |
| Autumn | Green Red | Yellow | Green | |
| Winter |
Position
- Full sun
- Partial shade
Aspect
South–facing or West–facing
Exposure
Sheltered Hardiness
H4Botanical details
- Family
- Asteraceae
- Native to GB / Ireland
- No
- Foliage
- Deciduous
- Habit
- Spreading branched, Clump forming
- Genus
Helianthus can be tall, erect annuals, tuberous or rhizomatous perennials, with coarse simple leaves and large daisy-like flower-heads
- Name status
Correct
How to grow
Cultivation
Grow in a moderately fertile, humus-rich, moist, well-drained, neutral to alkaline soil in full sun. May need support. See staking: perennials
Propagation
Propagate by seed or division. Divide established clumps every 2-4 years to both increase plants and retain vigour. See sowing seeds indoors for further advice
Suggested planting locations and garden types
- Cottage and informal garden
- Wildlife gardens
- Coastal
- Wildflower meadow
- Prairie planting
- Cut flowers
- Flower borders and beds
- Wall side borders
Pruning
Deadhead to prolong flowering
Pests
Diseases
May be susceptible to Powdery mildews and sclerotinia diseases
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